"The song 'Back to December' is an apology in the form of a song," the country star, 20, says in a new special, Taylor Swift: Speak Now, airing Thursday night on NBC. "You know, in life, you learn lessons. And sometimes you learn them the hard way. Sometimes you learn them too late."

She adds: "The song 'Back to December' is about a lesson I learned too late. And I think, when you do that, and you finally realize that you were wrong, you need to say you're sorry. And this was the best way that I knew how."

The lyrics of the song include the lines, "So, this is me swallowing my pride/Standing in front of you saying I'm sorry for that night."

Swift has not explicitly said the song is about the Twilight heartthrob, but she told E! News in October: "The person I wrote this song for deserves this. This is about a person who was incredible to me – just perfect to me in a relationship – and I was really careless with him."